ES2821734T3 - Overflow molten metal transfer pump with gas and flux introduction - Google Patents

Abstract

A method of fluxing or degassing a molten metal residing as a bath in a furnace, said molten metal bath having a surface height of the bath, the method comprises providing a refractory body, which forms an elongated generally cylindrical tube to raise the minus a portion of the molten metal above said height of the bath surface, whereby in the upper portion of the tube a volute-shaped chamber is provided to direct the molten metal vortex created by the rotation to an outward impeller into a channel and introducing at least one of a fluxing agent and an inert gas to the raised portion of the molten metal in the region of the volute chamber and / or the channel.

Description

DESCRIPTION

Overflow molten metal transfer pump with gas and flux introduction

Background

The present exemplary embodiment relates to a molten metal pump having gas and / or flux introduction capabilities. Find a particular application in conjunction with an overflow transfer pump style, and will be described with a particular reference to it.

Pumps for pumping molten metal are used in furnaces in the production of metal articles. Common functions of the pumps are circulating molten metal in the furnace or transferring molten metal to remote locations. The present description focuses on molten metal pumps for transferring metal from one location to another. It is of particular relevance for systems where molten metal is raised from a furnace bath to a tundish system.

Today, many metal mold casting facilities employ a main hearth that contains most of the molten metal. Solid bars of metal may be cast periodically in the main hearth. A transfer pump can be placed in a well adjacent to the main fireplace. The transfer pump draws the molten metal from the well and transfers it to a casting ladle or chute, and from there, to the molds that form the metal items. The present disclosure relates to pumps used to transfer molten metal from a furnace to a mold casting machine, ingot mold or the like.

In aluminum foundries where castings are manufactured using either high pressure casting or gravity casting techniques, casting ladles are often used to transport premeasured amounts of the liquid metal from a holding furnace. to a casting machine and then pouring the liquid metal into a receptacle of the casting machine. The casting ladle can be filled using a molten metal transfer pump to move the metal from the furnace to the casting ladle. A particular molten metal transfer pump described herein is referred to as an overflow transfer pump. For example, the overflow transfer pump in US Publication No. 2013/0101424, incorporated herein by reference, is suitable. Document EP 0095645 A1 discloses a method and a corresponding apparatus comprising melting the metal in a melting vessel. It is also proposed that processes such as degassing or adding flux be carried out in the melting vessel. Document EP 0 095 645 A1 teaches that metal can be transferred from the casting vessel to the mold by means of an electromagnetic type pump or a pneumatic type pump and preferably a pump as described in the description and drawings of document GB-A -2107132.

US 2010/0104415 A1 discloses a molten metal pump that creates a molten metal vortex within a pump standpipe to lift molten metal for lifting, transferring, mixing and / or melting applications.

US 2002/185790 A1 discloses metal level detection with a sensor / controller.

Molten metals such as aluminum can include traces of oxide and / or nitride that have a negative effect on the solidification of the particular alloy. A flux addition procedure is a methodology used to remove such impurities. Flux injection is the procedure of introducing a mixture of powdered or granulated salt, such as chloride and / or fluoride, into molten aluminum. Traditionally, the addition of salt flux has been introduced simply by depositing the flux in a foundry ladle before or during the addition of the molten metal and / or using a rotary apparatus for introducing the flux into the foundry ladle or downstream of the ladle. casting ladle.

An exemplary rotary apparatus includes a central hollow shaft attached to a rotor inserted into a pool of molten aluminum and rotated so that the salt flux travels down the hollow shaft and disperses into the molten aluminum through the rotor openings. . This style of flux injection device has proven to be problematic, as failure to control the flow rate of the purge gas used to keep molten metal off the shaft during insertion into the bath can cause splashing of the molten metal. Similarly, the high-flow process gas used after insertion can cause molten metal to splash. Conversely, an interruption in the gas supply line (for example, kink or kink) has the cascading effect of allowing the flux injection rotor / shaft assembly to become clogged with flux and / or the inlet of the flux. molten metal. Also, since the traditional device's rotor / shaft assembly is disposed below the molten metal line, improper handling can result in hardening of the metal therein, causing the device to stop working.

The addition of flux by a simple deposit in the foundry ladle may not achieve a homogeneous dispersion of the flux throughout the molten metal. In addition, the use of a rotary flux adding apparatus in the casting ladle or at a downstream location introduces an undesirable time delay to the casting process.

The molten or liquefied form of aluminum also attracts the formation and absorption of hydrogen within molten aluminum. Hydrogen develops as porosity during the solidification of aluminum alloys and is detrimental to the mechanical properties of the solid alloy. Degassing is an effective way to reduce porosity caused by hydrogen. An example of degassing involves the introduction of an inert gas such as argon or nitrogen into molten aluminum to collect hydrogen and non-metallic inclusions. The gas bubbles to the surface with hydrogen and other inclusions. Similar to flux addition, this procedure has historically been performed in the foundry ladle and / or in a downstream processing station. Consequently, undesirable time delays occur.

The present disclosure is directed to a system for introducing flux and / or gas to molten metal in a highly efficient manner. Furthermore, the present system is believed to provide comparable flux introduction results while improving efficiency and safety. The present disclosure is directed to an improved and more efficient introduction of flux and / or inert gas into the molten metal transfer pump prior to filling of the foundry ladle. Furthermore, it has been discovered that a more homogeneous mixing of flux within the molten metal can be achieved by introducing small amounts of flux over time into a moving stream of the metal. Similarly, it has been discovered that the quality of the metal can be improved by introducing an inert gas at the beginning of the process of transferring the metal from the furnace to the smelter. Exemplary locations for flux / gas injection may include the column of an overflow transfer pump or the second chamber of the split chamber overflow transfer apparatus or the tundish into which the molten metal is directed.

Summary of the invention

Various details of the present disclosure are summarized below to provide a basic understanding. This summary is not a comprehensive overview of the disclosure and is not intended to identify certain elements of the disclosure or to delineate the scope of the disclosure. Rather, the primary purpose of this summary is to present some concepts of the disclosure in a simplified form prior to the more detailed description that follows.

According to a first embodiment, a method is provided for adding flux or degassing a molten metal that resides as a bath in a furnace. The molten metal bath includes a height of the bath surface and the method provides at least one rotating impeller in the molten metal bath to initiate a flow of molten metal. The flow in the molten metal results in the elevation of a portion of the molten metal above the height of the bath surface where at least one of a fluxing agent and an inert gas is introduced into the raised portion of the molten metal.

According to a second embodiment, an apparatus is provided for introducing flux into molten metal residing as a bath in a furnace. The molten metal bath includes a height of the bath surface. The apparatus includes at least one rotary impeller in the molten metal bath to initiate a flow of molten metal, and the flow of molten metal causes at least a portion of the molten metal to rise above the height of the bath surface. Also provided is a device that introduces a fluxing agent into the raised portion of the molten metal.

According to another embodiment, an apparatus is provided for introducing gas into molten metal which resides as a bath in a furnace. The molten metal bath includes a height of the bath surface. The apparatus includes at least one rotary impeller in the molten metal bath to initiate a flow of molten metal, and the flow of molten metal causes at least a portion of the molten metal to rise above the height of the bath surface. Also provided is a device that introduces a gas into the raised portion of the molten metal.

Brief description of the drawings

It should be understood that the detailed figures are for the purpose of illustrating exemplary embodiments only and are not intended to be limiting. Furthermore, it will be appreciated that the drawings are not to scale and that some parts of certain elements may be exaggerated for the purpose of clarity and ease of illustration.

Figure 1 is a perspective view showing a flux introduction molten metal transfer system including the pump disposed in a furnace compartment;

Figure 2 is a partially cross-sectional perspective view of the pump of Figure 1;

Figure 3 is a side cross-sectional view of the pump shown in Figures 1 and 2;

Figure 4 is a perspective view of the pump chamber;

Figure 5 is a top view of the pump chamber;

Figure 6 is a view along line 6-6 of Figure 5;

Figure 7 is a perspective view of the upper section of the impeller;

Figure 8 is a perspective view of the assembled impeller;

Figure 9 is a perspective view of a flux injection assembly;

Figure 10 is a cross-sectional side view of the flux injection assembly;

Figure 11 is a perspective view of an alternative flux introduction molten metal transfer system;

Figure 12 is an enlarged view of the flux adding apparatus of Figure 11;

Figure 13 is a cross-sectional view of the apparatus of claim 12; Y

Figure 14 is a perspective view of a gas introduction apparatus.

Detailed description

The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will be apparent to those who read and understand the present detailed description. It is to be understood that the exemplary embodiment is construed to include all modifications and alterations that fall within the scope of the appended claims or the equivalents thereof.

Referring to Figures 1-3, a molten metal pump 30 is depicted in association with a furnace 28. The pump 30 is suspended through a metal frame 32 that is supported by the walls of the furnace compartment 34. The compartment from furnace 34 will receive molten metal from main furnace 28. In a typical scenario, molten metal will reside at a level as indicated by the bath level (BL, see Figure 3) throughout furnace 28 and furnace compartment 34 As used herein, the height of the bath level will refer to the top surface of the molten metal influenced by gravity, as it is within the main furnace 28 and in the furnace compartment 34. The bath level It may vary based on the amount of molten aluminum present in the furnace at any particular time, but will normally be above the lowest extent of pump 30 and below the top extent of the walls that form the furnace. oven compartment 34.

A motor 35 (see Figures 2 and 3) rotates a shaft 36 and attached impeller 38. Motor 35 has been omitted from Figure 1 to facilitate illustration of a flux introducing apparatus as described below. A refractory body 40 forms an elongated generally cylindrical tube 41 or pump chamber. The refractory body can be formed, for example, from fused silica, silicon carbide, or combinations thereof. Body 40 includes an inlet 43 that receives impeller 38. Preferably, bearing rings 56 are provided to facilitate uniform wear and rotation of impeller 38 therein. In operation, molten metal is drawn into the impeller through the inlet (arrows) and is forced upward into tube 41 in the form of a forced vortex ("equilibrium"). At the top of tube 41 a volute-shaped chamber 42 is provided to direct the molten metal vortex created by the rotation of the impeller outward in channel 44. Channel 44 can be joined / coupled with channel members or tubes tools to direct molten metal to its desired location, such as a casting apparatus, casting ladle, or other mechanism known to those skilled in the art. A flux introduction apparatus 45 (only shown in Figures 1 and 5) is placed in this region. Apparatus 45 can generally be located anywhere from its depicted location to downstream at point X.

Although shown as a volute-shaped cavity, an alternative mechanism could be used to deflect the rotating molten metal vortex into the channel. In fact, a tangential outlet that extends even from a cylindrical cavity will achieve a flow of molten metal. However, a diverter such as a fin that extends into the flow pattern or other element that directs molten metal into the channel may be preferred. This would not change the installation of the flux introducer in this region.

Turning now to Figures 4-6, tube 41 is shown in greater detail. Figure 4 shows a perspective view of the refractory body. Figure 5 shows a top view of the volute design and Figure 6 a cross-sectional view of the generally cylindrical and elongated pumping chamber. Figure 5 provides an illustration of the range of locations for flux adding apparatus 45. These views show general design parameters where tube 41 is at least 1.1 times larger in diameter, preferably by at least about 1.5 times, and most preferably, at least about 2.0 times larger than the diameter of the impeller. However, for higher density metals such as zinc, it may be desirable for the impeller diameter relative to the pumping chamber diameter to be in the lower range of 1.1 to 1.3. Furthermore, it can be seen that the tube 41 has a length significantly greater than the height of the impeller. Preferably, the length (height) of the tube is at least three times, more preferably at least 10 times greater than the height of the impeller. Without being limited by theory, these dimensions are believed to facilitate the formation of a desirable forced vortex ("equilibrium") of molten metal as shown by line 47 in Figure 6.

Figures 7 and 8 depict impeller 38 including an upper section 46 having vanes 48 supplying the induced molten metal flow and a bushing 50 for engagement with shaft 36. In its assembled condition, impeller 38 is coupled via spindles, bolts or pins / cement to an input guide section 52 having a hollow center portion 54 and bearing rings 56. The impeller can be constructed of graphite or other suitable refractory material. It is envisioned that any traditional cast metal impeller design would be functional in the present overflow vortex transfer system.

Referring to Figure 9, an assembly example of the flux injector 45 is shown in detail. The flux adding apparatus 45 is of the type described in International Application Publication WO 2012/170604, incorporated herein. as reference. The assembly 45 is supported by a structural base 112 that maintains the flux injector assembly 110 in a vertical position. As used herein, the term "flux" can be used to refer to a granular particulate material. An exemplary grain size of a molten flux ranges from about 1mm to about 6mm. The present apparatus is also suitable for use with mixed flux compositions. Exemplary flux compositions can include potassium manganese chloride, fluorides, and mixtures thereof.

The flux injector assembly 110 includes a pressurized tank 114 in communication with an isolation mechanism 118. In one embodiment, the isolation mechanism 118 is secured to the structural base 112 and configured to isolate the tank 114 from an inert gas flow. direct and independent to the lance that can be placed in the molten metal flowing into the volute chamber 43 or channel 44 (not shown). In addition, mechanism 118 includes a pneumatic valve to control the pressure within tank 114 and prevent back flow of molten liquid from entering the hollow shaft.

The pressurized tank is a generally sealed enclosure with a cylindrical body 120 having an opening 122 closed by a cap 124 secured at a first end 126 and a second end 128 that is disposed opposite the first end 126. In one embodiment, the Opening 122 is configured to receive flux and includes a screen to prevent foreign material or flux lumps from entering tank 114. Pressurized tank 114 is adapted to store a quantity of flux under controlled pressure. Provided in an enclosure 132 is a controller 130, such as a programmable logic controller (PLC) computer based on an electrical and gas control panel. In one embodiment, controller 130 is mounted to frame 112. However, controller 130 may be provided at a location remote from frame 112. Controller 130 may be in communication with the motor that drives the metal pump. molten metal 30 and with various sensors to determine molten metal levels and / or flow rates or volumes within pump tube 41 and / or channel 44. Similarly, the controller can be located remote from flux injection assembly 45. In addition , the controller may be associated with the pump and in communication with the flux injection assembly.

The pressurized tank 114 may be provided with at least one sight glass 134 in the barrel 120 for visual verification of the internal operation of the assembly 110. More particularly, the sight glass 134 allows the user to inspect the flux flow therein and identify the fluxes. components that function properly within tank 114. In one embodiment, pressurized tank 114 is designed to operate at a threshold pressure of less than fifteen (15) pounds per square inch gauge (psig). In another embodiment, pressurized tank 114 is operated at a working pressure between two (2) psig and ten (10) psig. Pressurized tank 114 includes redundant pressure relief valves 136 to prevent an undesired level of pressurization. A tank drain 138 is also provided to empty or clean assembly 110. In one embodiment, the tank is constructed of a powder coated material to prevent corrosion and clogging due to the interaction of flux and other chemicals.

Referring to Figure 10, tank 114 includes a feed mechanism 140 positioned within pressurized tank 114 in communication with a storage tank 150. Feed mechanism 140 operates to receive flux from storage tank 150 at an inlet. outlet 142 and discharge a predetermined quantity of flux from a feed outlet 144. The feed outlet 144 is spaced above a manifold 146 located adjacent the second end 128 of the pressurized tank 114 to receive the predetermined quantity of flux from the outlet. supply 144. Manifold 146 is connected to conduit 148 in a sealed manner to allow transfer of flux from tank 114 to isolation mechanism 118 located on structural base 112. Isolation mechanism 118 may, in turn, deliver the measured amount of flux to a lance 171 that directs the flux addition to chamber 43 and / or channel 44. Multiple lances can be used.

Storage tank 150 is positioned within pressurized tank 114 adjacent to opening 122 at first end 126 of pressurized tank 114 so that additional flux can be provided through opening 122. Cap 124 is provided in opening 122 to provide a sealed fit to prevent moisture from accumulating within tank 114 and to prevent excess flux and fumes associated with the flux from being released from inside storage tank 150. In one embodiment, the storage tank 150 includes a conical-shaped base 152 that abuts an interior wall 154 of tank 114. Storage tank 150 is defined by the area within interior wall 154 between the first end 126 and the conical-shaped base 152. The Conical shaped base 152 is configured to allow flux to accumulate in an opening in base 156 that is in communication with the feed inlet 142 of the feed mechanism 140. The storage tank 150 may include a surge tube 155 in fluid communication with the lower portion 157 of the pressurized tank 114 to allow for equalization. pressure while preventing unwanted flux transfer. In one embodiment, storage tank 150 is adapted to hold approximately 100 pounds (45.36 kilograms) of flux.

The at least one sight glass 134 allows the user to view the feed mechanism 140 while operating within the pressurized tank 114. In addition, the hoses 116a and 116b are adapted to communicate between the isolation mechanism 118 and a gas / pneumatic controller (not shown ). Hose 116a is a gas bypass line for inert gas flow where hose 116b is a pneumatic control supply line for actuating a valve in isolation mechanism 118. Controller 130 is configured to control level pressure within tank 114 and to identify and transmit an audible sound or alarm signal to indicate an over-pressurization condition of tank 114. The over-pressurization alarm signal may indicate the existence of a shaft obstruction within the system. downstream of isolation mechanism 118, particularly in conduit 148.

Controller 130 (such as a computer) is adapted to monitor and operate the flux injector assembly 110. Controller 130 can manipulate feed mechanism 140, isolation mechanism 118, and adjust the pressure level within pressurized tank 114 Controller 130 manipulates feed mechanism 140 to provide a predetermined amount of flux from inlet 142 to outlet 144 and will be described in more detail herein. A first optical sensor 158 is provided adjacent the base opening 156 to monitor the level of the flux in the storage tank 150. The optical sensor 158 sends a signal to the controller 130 that indicates the level of the flux within the tank 150. Optionally , a second optical sensor 159 may be provided adjacent the feed outlet 144 of the feed mechanism 140 to communicate with the controller 130 to reflect that the flux is transferred through the feed outlet 144.

The controller can provide precise flux dosages during various conditions. In addition, the controller can simultaneously control the pump and flux adding device. In addition, the controller will know the smelter ladle size to fill, the molten metal flow rates, and the metal flux requirements. The flux addition system provides intended flow by controlling the rotational speed of the impeller pump. A positive feedback loop system is used to control the speed of the pump so that the level and / or flow is as programmed. If the level and / or flow drops below the set point, the motor speed increases. These adjustments can be made several times per second and only stop when the level is at the desired level or if a previously programmed minimum or maximum speed is exceeded. By being able to control the outflow and control the flux introduction rate, the level of flux introduction required is predicted and controlled. Furthermore, these two characteristics are correlated to achieve a precise level of flux introduction during approximately the entire period of flow of the molten metal to fill the associated foundry ladle.

Similarly, the controller is programmed to begin the introduction of flux. In addition, the controller can determine when to start the flux adding apparatus based on the time and rate of initiation of the molten metal impeller and the speed. In particular, it is desirable that the introduction of flux begins only after (but shortly after) the flow of molten metal has reached the location of the flux adding apparatus. In addition, the controller will be able to determine the size of the casting ladle and calculate the desired level of flux introduction. The controller can determine a molten metal flow rate and estimate a fill time at that rate for the molten metal flow. The desired amount of flux can be distributed during this period for a homogeneous introduction.

Referring now to Figures 11-13, an alternative flux feed apparatus 201 is depicted. The flux feed apparatus 201 includes a support plate 203 secured to the mounting frame of the motor 205 of the overflow transfer pump. 207. The overflow transfer pump 207 is similar to the type illustrated above, including a motor 209 coupled to a driveshaft 211 that is secured to an impeller (not shown) disposed at a base end 213 of the elongated pump tube. 215. Rotation of the shaft and impeller within pump tube 215 results in the formation of a molten metal vortex that rises upward within tube 215 where it is received in a volute chamber 217. A rotational flow is created of molten metal within volute chamber 217 with molten metal exiting through outlet 219 into tundish 221. Flux is introduced into molten metal flowing through tundish 221 from flux feed apparatus 201.

It is noted herein that the flux feeding apparatus may alternatively be located so that flux is introduced into outlet 219 or into volute chamber 217 or on top of tube 215.

The flux feed apparatus 201 includes a hopper chamber 223 covered by a lid 225. The hopper chamber 223 may include an inverted truncated pyramidal section 231 that helps channel the particulate flux to a feed section 233. The flux is drives from the feed section 233 by a drive spindle (or multiple drive spindles) at an elbow connection 235 in communication with a gravity feed tube 237. The flux exits the gravity feed tube 237 and is deposited on the molten metal flowing into the tundish 221.

In certain embodiments, it may be beneficial for the gravity feed tube 237 to terminate at a level above the surface of the molten metal within the tundish 221 so that no gas feed is required and the shortcomings of the art are avoided. above of subsurface introduction devices, such as clogging and / or freezing of the molten metal inside.

With specific reference to Figures 12 and 13, the feed mechanism 201 includes a motor housing 241 within which is disposed a drive motor (not shown). The drive motor can be, for example, a 1/20 horsepower Bison gear motor with a 12.9: 1 gear reduction. The drive motor output shaft 248 is secured by a drive coupling 243 to a first drive connector 245. Locking spindles 244 are provided to facilitate attachment of the drive coupling 243 to the motor output shaft 248. Fixation spindles 246 are similarly provided between the transmission coupling 243 and the first transmission connector 245.

The motor housing 241 is secured to the rest of the flux feeding apparatus 201 by a pair of support arms 247. The support arms 247 extend from the motor housing 241, through a gearbox 253, through of the hopper feed section 233, and are secured at a second end by nuts 271.

A first conveyor screw 249 is located within a screw passage 250 that may optionally terminate in an outlet for the flux addition to drip to the desired location of the flowing molten metal or to be secured to the elbow 235 and gravity feed tube. 237, as shown in Figure 11.

The first drive connector 245, driven by the drive coupling 243, is located within the gearbox 253. The gears 255 are provided to connect the first drive connector 245 with a second drive connector 257 (only the end of the itself is visible when it protrudes from gearbox 253 in Figure 12). Each of drive connectors 245 and 257 are threadedly attached to conveyor spindles, only spindle 249 is visible. However, it is noted that the twin conveyor screws can have a mating relationship between their respective vanes. The conveyor screws cooperate to push the flux from where it is received in the feed section 233 of the flux hopper 223 into the passageways of the cooperative twins 250 and 252. The twins can be beneficial as a mechanism to maintain the feeding apparatus relatively free of buildup. The components of the flux feed apparatus 201 can be freely assembled by the use of releasable clamps such as the Destako style clamp 256 which joins the hopper section 231 to the feed section 233 and a similar clamp 258 which joins the chute section. the hopper 231 to a bracket 259 that secures the sensor 263. Advantageously, this facilitates cleaning and maintenance of the hopper assembly.

Flux hopper 223 may be provided with a window 261 and a sensor 263 positioned adjacent to window 261, to facilitate monitoring of flux levels within flux hopper 223. The sensor shown is a capacitance sensor. However, an optical sensor, a laser sensor or any other type of sensor known to the person skilled in the art is equally applicable. Furthermore, it is feasible for an individual to be able to monitor a simple viewing window.

Each of the sensor 263 and the motor housing 241 may include a passageway 275 and 277 respectively, suitable for receiving a power line and / or a connection between them to the controller (see 130 in Figure 10 as an example). More particularly, such interconnection can facilitate cooperative operation of the flux feed rate with the flow rate of the molten metal. Similarly, such an interconnection can facilitate the starting of the flux feed gear motor at a predetermined time after the start of the molten metal pump, so that the flux is introduced only when an appropriate flow of molten metal occurs. Similarly, the gear motor can be stopped before the corresponding cessation of operation of the molten metal pump motor, so that the flux feed does not continue after the flow of molten metal has been terminated. Also, premature or delayed introduction of flux can be wasteful and damage associated equipment.

It is further envisioned that the flux injection assembly may be an alternative device, such as a rotating wheel or other apparatus that facilitates the introduction of a fixed amount of flux for a predetermined period of time. In summary, the specific mechanics of the flux addition apparatus may not be critical to the success of the process. In this regard, a simple gravity feed flux supply apparatus (as opposed to gas injection) can be used which can dispense a measured amount of flux.

Furthermore, as shown in Figure 14, it is envisioned that degassing may be performed in elongated tube 340, volute chamber 342, and / or channel 344. For example, inert gas may be introduced by one or a plurality of lances 301. With respect to introduction into elongated tube 340, it may be desirable that the introduction of gas be at a level above the level of the molten metal bath BL (see Figure 3). The spears 301 are in fluid communication with a controlled gas introduction source 303 of the type often used in molten metal processing apparatus. Alternatively, or in addition, inert gas may be introduced through shaft 336 for introduction through impeller 338. For example, a hollow shaft and gas introduction device of the type disclosed in US 8,178,036, incorporated herein As a reference, it could be applied to the shaft drive system of the present molten metal pump 330. However, it is envisaged that the gas source 303 and / or the gas control apparatus associated with supplying gas to a shaft assembly / impeller would be in communication with at least one of a flux adding apparatus and / or a pump motor controller so that the gas introduction level can be adjusted based on the flow rates and / or volumes of molten metal.

It is also envisioned that gas source 303 (or an alternative gas source) could be used to supply an inert gas to chamber 342 and optionally to channel 344 to provide a protective gas for the floating cover. In addition, the inert gas in the floating cover can provide a barrier to prevent undesirable oxidation.

Another reciprocating transfer pump is described in US Published Application 2008/0314548, incorporated herein by reference. The system comprises at least (1) a container to retain the molten metal, (2) a dividing wall (or overflow wall) inside the container, the dividing wall having a height H1 and dividing the container into at least a first chamber and a second chamber, and (3) a molten metal pump in the container, preferably in the first chamber. The second chamber has a wall or opening with a height H2 that is less than the height H1 and the second chamber is juxtaposed to another structure, such as a casting ladle or tundish, to which it is desired to transfer the molten metal from the container. . The pump (be it a transfer, circulation or gas release pump) dips into the first chamber (preferably) and pumps the molten metal from the first chamber past the dividing wall into the second chamber, causing the level of molten metal in the second chamber rises (as used herein, this second chamber is sometimes referred to as a lift chamber). When the level of molten metal in the second chamber exceeds the height H2, the molten metal flows out of the second chamber into another structure, such as a tundish. The use of a flux adding apparatus and / or an inert gas introducing apparatus of the type described above, to introduce flux and / or gas into the transfer channel (e.g., tundish) of the device can provide advantages in the treatment of molten metal. Similarly, it is envisaged that gas and / or flux addition can be introduced into the second chamber of the apparatus. The equipment described above would be suitable for this purpose.

A further style of pump suitable for use in association with the present disclosure is an electromagnetic pump. In particular, magnetic repulsion is used to propel a conductor such as aluminum in which aluminum acts as the rotor while a coil acts as a stator. The induced magnetic flux drives the aluminum through a pump tube in the direction dictated by the plurality of stress. By changing the applied voltage, the velocity of the aluminum flow can increase or decrease. In this regard, an electromagnetic pump of the type available from Pyrotek's EMP Technologies of Burton-on-Trent, Staffordshire, UK can be used to provide a treatable elevated molten metal in association with the present disclosure. US Patent 5,350,440, incorporated herein by reference, provides a description of the use of an electromagnetic pump in association with a furnace containing molten aluminum.

Another suitable mechanism for use in association with the present disclosure is equipment that displaces molten metal, such as aluminum, within a metering container using a compressed gas. For example, the device disclosed in International Application No. WO 99/59752, the disclosure of which is incorporated herein by reference, provides a suitable apparatus for use in association with the present disclosure. It is further noted that pressurized gas appliances suitable for use with the present disclosure are available from STRIKOWESTOFEN of New Zealand, Michigan. More particularly, these gas displacement devices are envisioned to be suitable for lifting a molten metal for further treatment of the flux and / or inert gas.

Example

The apparatus depicted in Figures 11-13 was tested in a typical foundry environment. First, it was determined that 1,200 pounds of molten aluminum transferred to a foundry ladle using an overflow transfer pump without any treatment produced about 10 pounds of slag with a metal content of about 90%. Second, in a test using the present flux addition apparatus, approximately 0.75 pounds of Pyroflux 115 was added and the slag was reduced to approximately 3 pounds total with an estimated metal content of only 20-30 %.

Claims (11)

A method of fluxing or degassing a molten metal residing as a bath in a furnace, said molten metal bath having a bath surface height, the method comprises providing a refractory body, which forms an elongated, generally cylindrical tube for raising at least a portion of the molten metal above said height from the bath surface, whereby in the upper portion of the tube a volute-shaped chamber is provided to direct the molten metal vortex created by the rotation to an impeller outward into a channel and introducing at least one of a fluxing agent and an inert gas to the raised portion of the molten metal in the region of the volute chamber and / or the channel. 2. The method of claim 1, wherein said method comprises the introduction of a fluxing agent. 3. An apparatus for introducing flux or gas into molten metal residing as a bath in a furnace, said molten metal bath having a surface height of the bath, the apparatus comprising - at least one refractory body, which forms a generally cylindrical elongated tube, whereby the body includes an inlet containing a rotating impeller in the molten metal bath to initiate a flow of said molten metal, whereby a volute-shaped chamber is provided at the top of the tube, whereby the molten metal that is raised by the rotation of an impeller is directed outward in a channel, - and a device that introduces a fluxing agent or a gas into the raised portion of the molten metal in the region of the upper part of the tube and / or the channel. The apparatus according to claim 3, wherein said flux introduction device comprises a hopper, at least one feed mechanism and at least one supply conduit. The apparatus according to claim 4, wherein said feed mechanism comprises a wheel and a screw conveyor. The apparatus according to claim 3, further comprising a flux level sensor. The apparatus according to claim 3, further comprising a controller. The apparatus according to claim 7, wherein said controller monitors at least one of the molten metal flow, the flux level, the flux feed rate, and the molten metal pump speed. The apparatus according to claim 8, wherein said controller is programmed to interrupt the introduction of flux substantially simultaneously with or prior to cessation of the rotation of the molten metal impeller. The apparatus according to claim 8, wherein said controller is programmed to initiate the introduction of flux after the start of the rotation of the molten metal impeller. The apparatus according to claim 3, wherein said flux introducing device includes a support member secured to a motor bracket, said motor bracket supporting a motor that provides rotation of the impeller.